The present invention relates to a semiconductor IC device fabricating method and, more particularly, to techniques using electron beam resists and effectively applicable to processing a minute IC pattern.
An exposure process for forming a desired IC pattern on a semiconductor wafer among those of a recent method of fabricating a semiconductor IC circuit device employs an exposure technique using an electron beam instead of ultraviolet rays. An electron beam direct writing system, which writes IC pattern directly on a semiconductor wafer coated with an electron beam resist film with an electron beam, has attracted a great deal of attention because of its capability of forming a minute IC pattern on a semiconductor wafer superior to that of the conventional optical exposure system which transfers an IC pattern formed on a photomask on a semiconductor wafer.
The electron beam direct writing system, differing from the optical exposure system which transfers all the portions of an IC pattern formed on a photomask fully onto a semiconductor wafer, writes an IC pattern on a semiconductor wafer with an electron beam focused in a spot of a predetermined size. Therefore, it is a particularly important problem in carrying out the electron beam direct writing system to reduce the throughput of the IC pattern writing process.
A first factor that determines the throughput of the IC pattern writing process is time necessary for irradiating a resist film to form an exposed IC pattern in the resist film. Efforts have been made in various fields to develop an electron beam resist having improved sensitivity. A chemical amplification resist is an example of a recently proposed electron beam resist. When this chemical amplification resist is exposed to an electron beam, a free acid is produced therein and the free acid acts as a catalyst to promote exposure reaction when the resist is heat-treated after exposure to an electron beam.
This chemical amplification resist is mentioned in, for example, Journal of Photopolymer Science and Technology, Vol. 2, No. 1, pp.115-122 (1989).